Well I spent most of the past 3 days trying to work out why no videos were converting on one of my sites.
After blasting support messages to both my software developer and dreamhost support, it seems that DH are using ffmpeg version 0.8.17. The message from my developer support is the following:
"Your server uses an ancient version of FFMPEG.
Latest version is 3.0.2.
This is common issue. Please, ask your hosting provider to upgrade it to latest version.
Video conversion won't work with it."
I'm sure others may be experiencing such issues and I dread to think the possibility of old software being vulnerable to security vulnerabilities.